Disposable instruments for indicating the internal temperature of food products have been known for some time. One example of such a device is commonly referred to as a “pop-up” temperature indicating device, which includes a cylindrical housing and an indicator rod. The indicator rod is held in a retracted position in the housing by a fusible material, with the retracted position biased by a compressed coil spring. Upon achieving a predetermined temperature, the fusible material softens and looses its hold on the indicator rod. Upon release of the indicator rod from the fusible material, the spring decompresses and moves the indicator rod into an extended position out of the housing.
According to U.S. Pat. No. 5,323,730 entitled “Thermally Responsive Indicator With Organic Retaining Means” to Ou-Yang, the retaining material has typically comprised metal alloys, as in U.S. Pat. Nos. 3,140,611; 3,682,130; 3,693,579 and 3,713,416. The '611 patent, for example, refers to an alloy consisting of bismuth-52%, lead-40%, cadmium-8%, to which is added two parts of Wood's alloy. The '730 Patent goes on to indicate that, while devices employing such alloy retaining materials have proven useful, they have certain drawbacks. For example, such alloys are typically prepared from toxic metallic substances such as bismuth, lead, cadmium and tin.
While disposable temperature indicating devices have been used for indicating the internal temperature of food products, such devices have not been considered for use upon tissues of a living human body during surgery.
Some forms of surgery involve killing tissue to achieve a therapeutic result. The term “ablative surgery” as used herein refers to any of a variety of methods used to kill tissue, with one specific method comprising radio frequency ablation.
To be successful, ablation treatment may require a certain precision. The surgeon must target a particular region, and be careful not to cause unnecessary trauma to surrounding areas of the patient's body near the target area. Just as important, the surgeon must be confident that the procedure within the target area has been appropriately performed. For example, the surgeon may need to determine whether the tissue has been ablated.
What is needed is a disposable temperature indicating device suitable for use upon tissues of a living human body during surgery, particularly during surgery involving ablation.